The present invention relates to the handling of sheet materials and more particularly to a method of splicing successive rolls of plastic sheet materials to reduce the chances of breakage.
Meat and other food products are sometimes packaged in plastic wrappers or enclosures molded from plastic sheet materials such as polystyrene. In manufacturing such wrappers or enclosures, rolls of the plastic sheet material are printed with information and marketing material as the rolls are passed through rotary presses. To avoid the necessity of halting the printing operation in order to thread each roll through the printer, it is a common practice to splice the trailing edge of one roll with the leading edge of the next roll at the input side of the printer. After the plastic material is printed, the rolls are cut apart on the delivery side of the printing station and rewound on individual cores. The rewound rolls are then transported elsewhere to have individual wrappers or enclosures molded and stamped from the rolls of printed plastic material.
While the plastic materials have many advantages as packaging materials, they tend to be brittle. When rolls are separated after the printing operation by means of a cutting knife, the brittle plastic tends to shatter, wasting processed material and making it more difficult to rewind the rolls. The entire printing operation must be stopped in recovering from a break in the plastic material.
Most rotary presses have one or more drying stations which heat the printed plastic material to set the inks. When the printing operation is stopped due to a break in the plastic material, the plastic material halted within each of the drying stations is weakened by its exposure to a greater than normal amount of heat. When the printing operation is resumed, this material is more easily broken when placed under tension, compounding the problem.